Mammography currently is the screening device for breast examination, although the false-positive rate in it could be 66% or higher. Thus imaging ultrasound and biopsy must often be used for final diagnosis. However, ultrasound has potential for improved spatial resolution, and could provide features that mammography currently does not have: real- time viewing, 3-D imaging, absence of ionizing radiation, and characterization of mechanical properties of the tissue, which we propose to exploit with an advanced ultrasound scanner design. We propose the development of a new technology that will yield an operator-independent, very high-resolution, real-time imager with 3-D imaging capabilities. Our approach is to use a Phase I grant to determine the trade-offs in various methods for applying low F-number 1.5-D arrays with center frequencies of 5 MHz (or higher). Our methods will include B-scan, synthetic focusing with and without corrections for time of flight, and adaptive focusing using a maximum brightness method. The Phase I project will use an existing laboratory scanner to develop the trade-offs for the various methods for the construction of a clinical prototype scanner in Phase II. PROPOSED COMMERCIAL APPLICATIONS: This proposal will lead to a significant advancement in noninvasive breast cancer screening with non-ionizing ultrasound. It is expected to provide a scanner with higher sensitivity (more suitable to cancer screening) and with lower false positivities (fewer biopsies) and be a strong competitor in a potential billion dollar cancer screening market.